Use the default theme as the fallback UI in Blink

ui/native_theme/common_theme.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/native_theme/common_theme.h"
 
 #include "base/logging.h"
 #include "grit/ui_resources.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/skia_util.h"
 #include "ui/gfx/sys_color_change_listener.h"
 #include "ui/views/controls/menu/menu_config.h"
 
 namespace {
 
 // Theme colors returned by GetSystemColor().
 
 // MenuItem:
 const SkColor kMenuBackgroundColor = SK_ColorWHITE;
-const SkColor kMenuHighlightBackgroundColor = SkColorSetA(SK_ColorBLACK, 15);
+const SkColor kMenuHighlightBackgroundColor = SkColorSetARGB(15, 0, 0, 0);
 const SkColor kMenuHighlightBackgroundColor2 = SkColorSetRGB(0x42, 0x81, 0xF4);
 const SkColor kMenuInvertedSchemeHighlightBackgroundColor =
     SkColorSetRGB(48, 48, 48);
 const SkColor kMenuBorderColor = SkColorSetRGB(0xBA, 0xBA, 0xBA);
 const SkColor kEnabledMenuButtonBorderColor = SkColorSetARGB(36, 0, 0, 0);
 const SkColor kFocusedMenuButtonBorderColor = SkColorSetARGB(72, 0, 0, 0);
 const SkColor kHoverMenuButtonBorderColor = SkColorSetARGB(72, 0, 0, 0);
 const SkColor kMenuSeparatorColor = SkColorSetRGB(0xE9, 0xE9, 0xE9);
 const SkColor kEnabledMenuItemForegroundColor = SK_ColorBLACK;
 const SkColor kDisabledMenuItemForegroundColor = SkColorSetRGB(161, 161, 146);
@@ skipping 142 matching lines @@
     case NativeTheme::kColorId_FocusedMenuItemBackgroundColor:
       return kMenuHighlightBackgroundColor2;
     case NativeTheme::kColorId_SelectedMenuItemForegroundColor:
       return SK_ColorWHITE;
     default:
       return color;
   }
 }
 
 }  // namespace ui